Breadcrumbs

Admittance: the ocean's response, depending on the frequency, to the action of the generating force.

Age of the tide: time interval between the syzygy and the maximum range of tide that follows.

ALLENVI: Environmental alliance.

Altimetry: measurement of the height of water using spatial techniques.

Amphidromic points: points located at sea around which the tide wave appears to turn.

Amplitude: difference between the height of a high or low tide and the mean level. This term is often used in error to designate the range of tide.

Apparent time: true solar hour angle.

Argument number: method for designating the components of the tide, using a 6-figure number, making it possible to identify the astronomical parameters from which they are derived and deduce from them their period.

Ascending node: point at which the lunar orbit and the ecliptic intersect in the direction of movement of the Moon from the Southern to the Northern hemisphere.

B

Backrush current: current generated by the slope of the free surface, excluding the action of the tide.

Ecliptic latitude: angle between the celestial body and the ecliptic plane.

Ecliptic longitude: angle between the orthogonal projection on the ecliptic of the direction of the celestial body and the direction of the vernal point.

Ecliptic: the Earth's orbit around the Sun or the Sun's apparent orbit viewed from the Earth.

Ellipsoid: mathematical surface defining a geodetic system based on the relative positions of points located on the Earth's surface.

Equation of time: difference between the mean time and the true time. Species: set of components whose frequencies are close to a given number of cycles per lunar day. we distinguish between species with long periods, diurnal and semi-diurnal species.

Equator: terrestrial great circle contained within the plane perpendicular to the polar axis.

Equinoctial point: intersection of the ecliptic plane and the equator.

Equinoctial spring tide: maximum amplitude of the semi-diurnal tide around the equinoxes.

Establishment of the port: time (true time) of high water on a day on which syzygy occurs at apparent noon.

Mean Sun: fictitious celestial body having the same apparent period of revolution as the true Sun, but with uniform motion. The mean time varies by 0 to 24 hours from the passage of the mean Sun through the upper meridian.

Mean time: uniform time scale defined by the mean Sun. By definition, a mean time day is 24 hours in length.

Rule of sixths: expeditive method for calculating the current knowing its amplitude and the time of the maximum.

S

Saros: Period of 6585.3211 days corresponding to 223 lunations. At the end of this period, the Moon, the Sun, the node of the lunar orbit and the lunar perigee are in roughly the same relative situation.

Sidereal day: period of the Earth's rotation from vernal point to vernal point.

Sidereal revolution: time required for the mean longitude of the Moon, counted from a fixed equinox, to increase by 360°. It is equal to 27 days 7 hours and 43 minutes.

Situation: delay, measured as an angle between the maximum of the component and the maximum action of the corresponding element of the generating potential. This notion has been generalized for interaction components.

Spectral analysis: location in the frequency scale of the signals relating to the temporal variations of an observed magnitude.

Spectrum: graphic representation of the spectral component moduli.

Spring tide: maximum tidal range.

Stand: time interval during which the sea level remains practically stationary. Depending on the case we talk about low water stand and high water stand.

Swell: agitation of the surface of the water, with a regular crest that propagates roughly in the same direction as the others. When a perfect frequency is achieved, we talk of swell, swell being a series of identical, regular waves. In the absence of any clear organization, we talk of a choppy sea.

Synodic revolution: also known as the lunar month, it is the time interval between two full Moons and two new Moons.

Syzygy: moment at which the meridian planes of the Moon and the Sun are aligned. It corresponds to the Full Moon or the New Moon.

UPF: Université de Polynésie française (University of French Polynesia)

V

Vernal point: spring equinoctial point.

Vertical: direction of a plumb line. With a degree of approximation, it is considered to be sufficient for problems relating to tides, that the vertical intersects the polar axis at the centre of the Earth.

W

Wave velocity: The speed of propagation of the tide wave

Wave: agitation of the surface of the water, with a regular crest that propagates roughly in the same direction as the others. When a perfect frequency is achieved, we talk of swell, swell being a series of identical, regular waves. In the absence of any clear organization, we talk of a choppy sea.

X

Z

Zenith distance: angle between the direction of the zenith and the direction of the celestial body.

Zenith: the point where the direction of the PLUMB LINE produced above the HORIZON meets the celestial sphere (opposite of nadir).

ZH: Hydrographic datum.

Part of this Glossary is taken from the B. Simon's book (2007) "La marée. La marée océanique côtière" published by the Institut océanographique.